If an engine lubricating oil's viscosity is given as SAE 20W as compared to SAE 20, what is the significant difference between the two lubricating oils?
• Meaning of the W in SAE viscosity grades (e.g., 20W vs 20) • How oil viscosity changes with temperature (cold start vs normal operating temperature) • Difference between winter-rated oils and single-grade (non-W) oils
• Ask yourself: What does the W actually stand for in SAE 20W, and when is that property most important in engine operation? • Think about cold starts: Which oil grade will flow better at low ambient temperatures, and which is better only once the engine is hot? • Consider which oil would be chosen for a vessel that operates in both cold and warm climates throughout the year.
• Verify what SAE 20W indicates about viscosity behavior at low temperatures. • Verify what SAE 20 (without W) indicates about viscosity behavior at normal operating temperatures. • Check which option correctly pairs low-temperature (winter) performance with year-round vs high-temperature-only use.
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